超聲測(cè)距中的偽隨機(jī)碼渡越時(shí)間的捕獲

超聲測(cè)距中的偽隨機(jī)碼渡越時(shí)間的捕獲

采用數(shù)字相關(guān)的方法確定超聲波測(cè)距中的渡越時(shí)間。借助于一個(gè)經(jīng)過適當(dāng)選擇的偽隨機(jī)序列信號(hào)作為超聲波的發(fā)射信號(hào),可以通過數(shù)字相關(guān)方法求出發(fā)射序列和接收序列的相位差,即渡越時(shí)間。本文在計(jì)算自相關(guān)函數(shù)時(shí)放棄了快速傅立葉變換( FFT) 算法,省去了乘法運(yùn)算,取而代之的是只用異或和加法的并行數(shù)字相關(guān)技術(shù),它顯著地減少了數(shù)據(jù)處理時(shí)間和
FPGA 資源。系統(tǒng)以Altera 公司的quartus Ⅱ?yàn)殚_發(fā)平臺(tái),經(jīng)邏輯綜合、布局布線后,適配到FPGA 芯片中,給出了仿真結(jié)果。

Digital correlation approach is used to find t he time of flight (tof) in ult rasonic distance measure2 ment . Wit h t he help of an adequately chosen Pseudo random Number ( PN) as t ransmit ting signal of t heult rasonic sensor , t he time of flight can be got by using digital correlation approach to fine t he p hase differ2 ence between t ransmit ting sequence and receiving sequence. The correlation f unction is comp uted by usingxor and add operation taking place of FF T algorit hm using multiplication. This met hod shortens t he pro2
cessing time and FPGA resource. The system design is based on Alet ra’s quart us Ⅱsof tware , and described by V HDL language and be fit ted to FPGA chip af ter logic synt hesizing and placement routing. The timing simulation result in placement and routing is also presented.